The BioGRID CORE is the largest component of the BioGRID architecture in terms of size and volume of data stored. It consistes of 26 tables that contain more than 74 million records. Our primary annotation information is stored and maintained in the CORE and is updated frequently from a large number of public resources including Entrez-Gene, UniprotKB, FlyBase, SGD, WormBase, MGD, OMIM, Ensembl, PSI, ZFIN, HPRD, TAIR, EcoCYC, PubCHEM, Pubmed, Gene Ontology, and more. The CORE is the foundation of our web-based interfaces and contains the data used for the primary quality control of our annotation. The BioGRID CORE tracks additions and deprecations of annotation data and acts as the main conduit between the IMS and the WEB, which both utilize the CORE in their functionality.